az login uses cmd.exe when using WSL which doesn't support UNC paths

[GarrettGeorge]

{
  "azure-cli": "2.0.80",
  "azure-cli-command-modules-nspkg": "2.0.3",
  "azure-cli-core": "2.0.80",
  "azure-cli-nspkg": "3.0.4",
  "azure-cli-telemetry": "1.0.4",
  "extensions": {}
}

Describe the bug
az login triggers error with cmd.exe:

CMD.EXE was started with the above path as the current directory.
UNC paths are not supported.  Defaulting to Windows directory.

This is because az login uses a function called open_page_in_browser. If az login is run inside of WSL the following command is run:
subprocess.call(['cmd.exe', '/c', "start {}".format(url.replace('&', '^&'))])
Based on how WSL handles this command, the current directory uses a UNC path for calling cmd.exe. A UNC path is a result of wslpath -w $(pwd) which converts the current WSL Linux path to a Windows compatible path.

An example output for wslpath -w $(pwd) is:
\\wsl$\Ubuntu\home\myusername

To Reproduce
Run az login while using Windows Subsystem Linux (WSL)

Expected behavior
No error from cmd.exe and the current directory in WSL works as expected.

Environment summary
azure-cli inside of WSL Ubuntu

Additional context
I think the solution is to use powershell instead of cmd.

The following is equivalent to the current cmd command:
subprocess.call(['powershell.exe', 'Start-Process', '-FilePath', "start {}".format(url.replace('&', '^&'))])

[jiasli]

Thanks for the feedback. We will look into it.

[yonzhan]

add to S165.